The present invention relates to new liquid delivery systems. More particularly, the invention relates to liquid delivery systems in which two or more liquid chemicals are to be delivered to two or more processing units, for example, laundry wash machines.
In the laundry industry, various liquid chemicals, such as detergents, bleaches, alkalis, acids and the like, are employed, often during different parts of the same wash cycle. The proper or desired amount of each of these liquid chemicals must be delivered at the correct time and in the correct sequence in the wash cycle. Quite often, the individual liquid chemicals are incompatible with one another, e.g., mixing of two or more of these materials can cause a violent and/or damaging reaction. In such circumstances, it is important that the liquid chemicals not be allowed to mix during delivery.
Because the laundry industry involves or uses large volumes of liquid chemicals, it is important that the delivery system functions without wasting these materials. Thus, it would be advantageous to provide a delivery system which can detect and warn of liquid chemical leaks.
In addition, the delivery system should be mechanically straightforward, reliable and provide reproducible delivery results.
Proudman U.S. Pat. No. 5,246,026 discloses a liquid delivery system which employs two flowmeters and compares the flows monitored by these two flowmeters in determining how much liquid chemical is delivered. This Proudman system has several disadvantages. In the first place, comparing the results obtained from two flowmeters requires that both meters be accurate in order that the comparison is correct. Continual flowmeter calibrations are required to provide such accuracy. Also, the Proudman system has no means for detecting liquid chemical leaks. Thus, the Proudman system is relatively expensive to install, operate and maintain, provides results which may not be accurate and can involve relatively large and expensive losses of liquid chemicals.